1. Field of the Invention
The present invention relates to a diaphragm valve; and more particularly relates to a weir-type diaphragm valve.
2. Brief Description of Related Art
FIG. 1 shows an example of a typical locking mechanism for a rotating system in the form of a spring-pin ratchet. In this example, the spring-pin ratchet has a rotating cover which moves along an axis of rotation, however, an axial translation is not required for the spring-pin ratchet mechanism to work. In FIG. 1A, the spring-pin ratchet has a spring-pin 1 fully engaged into a trough between teeth that form part of the ratcheting mechanism. Note that although the spring-pin 1 appears to be seated, the cover 2 has not been tightened. During the rotation, the spring-pin 1 rides over individual teeth, as shown in FIG. 1B. When fully tightened, the spring-pin 1 is flush; however the passive visual indication 3 for this system is the covering of the decal by the axial motion of the cover 2, as depicted in FIG. 1C. The ratcheting mechanism prevents unloading of the system until the pin 1 is pulled.
One disadvantage of the prior art technique shown in FIG. 1 is that there is not a conclusive indication that a final position of a multi-turn mechanism has been achieved when using a simple spring-pin ratchet mechanism. In the case of a diaphragm valve, customers demand a positive indication for both product and employee safety.